For some years now, the market has been requesting that vehicles be provided with an electric power system supplied at 48 Volt. A 48 Volt power supply has many advantages compared to a 12 Volt power supply and allows manufacturers to significantly improve the performances of hybrid vehicles or of vehicles provided with Start & Stop systems (in particular, in relation to the recovery of braking energy) and, especially, to remarkably reduce the currents absorbed by on board electric loads, thus improving at the same time electric efficiency. As a matter of fact, over the years we experienced an increase in the use of electric loads in cars, which consume high powers, in particular at low temperatures, and, therefore, when they are powered with a 12 Volt voltage, definitely absorb high currents. Given the same supplied power, having high absorbed currents circulating in the on-board system leads to technical complications (for example, you may need cables with a larger section or more powerful electric actuators with greater dimensions) and, as a consequence, to an increase in the costs to be borne.
Hence, an electric power system supplied at 48 Volt leads to advantages in the powering of all those devices characterized by high absorbed powers, such as for example electric heaters, liquid pumps, cooling fans, air conditioning systems, hi-fi systems, navigators, displays, etc. Therefore, different solutions were suggested, in which an auxiliary electric power system supplied at 48 Volt, typically a lithium-ion battery, assists the traditional electric power system supplied at 12 Volt. The two electric power systems supplied at 12 and 48 Volt, respectively, are connected to one another with a parallel configuration; between the two storage systems of the two electric power systems supplied at 12 and 48 Volt there is interposed an electronic power converter, typically a DC/DC converter, which allows energy to be transferred between the two storage systems in a preferential direction, in particular from the 48 Volt electric power system towards the 12 Volt electric power system, but there are also cases in which the DC/DC converter can transfer energy in both directions.
A dual-voltage power supply architecture—namely at 12 Volt and 48 Volt—allows manufacturers to have a greater electrical energy to both minimize inefficiencies and improve the performances of the vehicle, besides allowing manufacturers to use cables with a reduced section and with smaller dissipations, thus with a better efficiency.
However, against a quantity of available power that is even excessive, an electric power supply architecture with dual voltage at 12 Volt and 48 Volt, in which the two electric power systems powered at 12 and 48 Volt, respectively, are arranged in parallel, leads to a remarkable increase in the space taken up and in the expenses to be borne.